The present invention relates to ablation and exposure of flexographic printing plates, and more particularly to a system and method of continuously exposing a flexographic plate on a rotating cylinder that is also used to ablate the plate.
Digital flexographic printing plates are conventionally exposed in two steps. The first step is to ablate the plate in a pattern that defines a mask on the plate. The mask represents the graphical image that the plate is used to print. This step is typically performed by placing the plate on a rotating cylinder and ablating the plate with a linearly movable imaging source controlled to ablate the desired image into the overcoat of the plate. The second step of the process is to expose the thereby masked plate to high intensity light, which results in a plate that is ready for processing. This step is typically performed by placing the masked plate on a flatbed and flooding the plate with high intensity light.
In the conventional two step process, great care must be taken in handling the plate after it has been ablated and before it has been exposed, as the carbon on the plate can be easily scratched or otherwise blemished in a way that renders useless the image represented on the plate. Flexographic plates are expensive, and losing plates due to corruption resulting from handling is therefore quite undesirable. In addition, flexographic plates can also be quite large in some applications, requiring a very large flatbed exposure device which can also be quite expensive.
One approach to solving this problem has been to provide an exposing apparatus that is integrated into the ablation system. A high intensity light source is provided that is movable along the cylinder on which the plate is placed, exposing the plate after it is ablated as it rotates on the cylinder. Although the high intensity light source provides light continuously, this configuration effectively provides a temporary pulse of light to each point of the plate (the pulse beginning when the point on the plate rotates into the field of light and ending when the point on the plate rotates out of the field of the light). Repeated pulses of light are not as effective in exposing the plate as continuous exposure, making this solution less than ideal.
It would be an improvement in the art to continuously expose masked flexographic printing plates without having to handle the plates between the processes of ablation and exposure.